Erkka-

I looked into this thread and couldn't find the details about your description here. So '85'-'87 has the 25 mm TT, and '88 up has the 28mm. So I'm keenly interested here, but didn't see mention of the shims? Is this within the clamp? Any details are appreciated, and advance apologies for not catching it in the other thread.

Chris, my response was to Steen Jensen's question about front-back position of center shaft inside outer tube. It must be correct for rear clamp bolt to align properly in to the shaft groove. Specs I could find from WSM are in post #43.

How to determine shim for '78-'84 TT front end is also in WSM but not in said thread. I have understood '85-'87 have exact same TT center shaft and front flex plate as earlier 4sp cars. This means its possible to install same shims to these cars as well and virtually eliminate possiblity of TBF. In my opinion very cheap way to buy some peace of mind.

Thanks, I'll take a look at the WSM.

Hi Marton,

I have sent you a PM to answer your questions.

Constantine



[QUOTE=marton]Hi Constatine,

I think we have 2 different topics here, I am not questioning that your stronger clamp fixes the problem. I am questioning your theory about the cause.

My 88 has the circlip grove on the shaft. I installed the washers and circlip, pain in the butt. Not very much room to work.

Cheers,
Glenn

Is it also 28 mm thick (other than front and rear 5" of it)? Looking for time when shaft was changed or if in fact 28 mm has also grove.

The 28 mm shaft is the neck downed, shorter version that does not have the area needed to place the circlip, bearing and washers.

One thing to remember is torque tubes (TTs) have been changed and one should visually inspect their driveshaft to confirm which style they have before ordering these parts.

If one wants to install these parts the manuals have a formula to calculate the shim thickness needed to set the correct distance between the flexplate and flywheel.

Porsche stopped using this method for a reason. We believe the reason is the difficulty in setting up the correct distances and the problems Porsche techs in the field were having in doing so, sometimes causing TBF to befall customer cars. Porsche even sent a Porsche engineer to the U.S. and other countries to teach the field techs on the proper procedures of installing a TT.

For this reason we believe Porsche stopped using these pieces and changed the procedure to just leveraging the crank to the back of the car and then clamping the front pinch bolt as being one of the last steps of doing a TT change. This would ensure no forward pressure is being exerted onto the thrust bearing. It is our opinion Porsche did not take into full account the weakness of the front flexplate clamp in not being able to hold onto the driveshaft during operation.

Constantine

When we replaced Matt's (Edco) TT in his 91, we used the early shaft and the shim setup. The shims appear to be a challenge due to limted space to use a circlip plier. With a small plier, it is easy to place the clip on the shft from in front of the flywheel, through the cutouts. Utlimately, it only took a minute to get the clip on the end of the shaft, then prod it down the shaft into its groove.

The instructions for setting the clearance are confusing. My interpretation was there should be 0.3mm of play between the shim and the back of the flywheel. My further interpretation is that the idea of the small amount of clearance is to not exert any rear preload and to prevent the shaft from moving back much through the clamp by having such very little clearance. This is hard to measre directly, although it could be done with a long feeler gauge.

I suspected that to be case also but its possible Porsche did two versions of 28 mm. Probably not though as someone would have mentioned it before already.